This invention is directed to a miniature window particularly useful for the hermetic closure of the end of a protective sheath around an optical fiber.
U.S. Pat. No. 4,170,997 to Douglas A. Pinnow and Anthony L. Gentile is directed to a medical laser instrument which employs a flexible fiber optical endoscope which is suitable for application of long wavelength, high power laser radiation for surgical purposes inside the human body. To accomplish this purpose, the toxic, thallium halide optical fiber has a sheath which prevents contact between the body fluid and the fiber optic waveguide material which is capable of infrared transmission. When non-refractory optical fibers are used to transmit long wave infrared radiation, it is often necessary to protect them from a hostile environment and to protect the environment from their toxic effects. For example, fibers of alkali halides, while excellent transmitters of infrared radiation, are very soluble in water and easily corroded by moisture. Some other infrared transparent fibers are made of toxic thallium halides and it becomes necessary to protect the environment from this hazard. It is thus necessary to protect such fibers against body fluids and isolate body fluids from these poisonous substances. In either case, it becomes necessary to surround the fiber with a hermetic protective sheath while providing a means for the radiation to enter or emerge at the end of the fiber.